Policing by the numbers

Cambridge patrolman John Cameron walked his beat in Central Square. Serious crime fell last year to its lowest level since 1963, after historic lows were recorded in 2009 and 2010.
(jOSH rEYNOLDS FOR THE bOSTON gLOBE)

“In the old days, we used to randomly patrol neighborhoods,’’ Haas said. “Now, it’s very much directed. It’s very methodical. . . . It’s more about preventing future victimization.’’

Yet, while the overall number of serious crimes in the city was down by 1 percent from the year before - and 5 percent lower than the 5-year average, according to the department’s data - some categories of crime saw an increase, though the department said those spikes were not statistically significant.

In explaining the declines announced yesterday, Lieutenant Daniel Wagner, who heads the Cambridge Police Crime Analysis Unit, said his unit is able to identify upswings of a particular crime in a specific area or at a certain time.

For example, officers may see a spike in reported pickpocket incidents. By using data analysis, they could determine that most of the crimes occur between 2 p.m. and 4 p.m. in a particular square.

Using that information, officials can decide to assign more patrol officers to head off those crimes.

“I’m optimistic that we can continue to reduce crime,’’ Wagner said. “I think that we’re at somewhat of a tipping point in terms of developing more advanced, comprehensive ways to use predictive analytics for crime mapping.’’

One category that saw an increase in crime is homicides. There were no murders in Cambridge in 2010, but there were five in 2011.

Haas said those killings were mostly the result of domestic disputes that could not have been anticipated by police.

Commercial robberies also rose by 55 percent, from 22 in 2010 to 34 robberies in 2011.

People interviewed near the Central Square MBTA stop had mixed views on the state of the city’s safety.

Angel Vasquez, 41, was surprised to hear that crime is down. He has been working in Central Square since 2001, and from his perspective, things have gotten much worse in the past decade.

While he’s seen an increased police presence in the neighborhood, he continues to see people selling drugs outside his window. After dark, he always escorts a secretary from his office downstairs because he worries that violent people may be hiding in the stairwell.